The senior author of the study, Dr. Mark Olfson of the New York State Psychiatric Institute at the Columbia University Medical Center, was quoted in the New York Times story on this finding as saying, “I have been studying trends in mental health services for some time, and this finding really stands out as one of the most striking increases in this short a time.” It kind of gets your attention when the lead author of a study didn’t even expect the findings the research uncovered.

So what’s the explanation?

The authors clearly indicate two possible explanations:

The impressive increase in the diagnosis of childhood and adolescent bipolar disorder in US office-based practice indicates a shift in clinical diagnostic practices. In broad terms, either bipolar disorder was historically underdiagnosed in children and adolescents and that problem has now been rectified, or bipolar disorder is currently being overdiagnosed in this age group. Without independent systematic diagnostic assessments, we cannot confidently select between these competing hypotheses.

Yes, I can buy either of those. But there’s a third explanation not mentioned, and I can’t imagine why not.

In the study, researchers analyzed a National Center for Health Statistics survey, conducted during a one-week period of time, of office visits that focused on doctors in private or group practices. They key, to me, is that these are regular doctor’s offices. Not mental health professionals. Not professionals who are trained and experienced in diagnosing mental disorders, which often rely more on a clinician’s experience and expertise in asking the right questions to differentiate a disorder from something else.

The researchers just take it for granted that general practitioners are just as reliable diagnosticians for mental disorders are they are for medical concerns. But I have my concerns about this assumption, and it may help partially explain this result. I suspect that such general practitioners are more likely to diagnose a mental disorder, not out of any necessary ignorance or such, but because it is often the easiest thing to do than to try and get a parent a referral to a mental health specialist (such as a psychiatrist or child psychologist), and then ensure they followup with their appointment. There is research to back this up as well, as doctors who receive specialized training in specific disorders’ diagnosis and treatment do a better job of screening and diagnosing such disorders (see, for example, Hata, 2005).

It may be that the since these were regular medical doctors, and not mental health professionals, their diagnoses were simply more, well, wrong. Since this is a retrospective statistical study, we’ll never know the answer to this possibility. Future studies, however, should take this possibility into account in their design.

The researchers, eventually, acknowledge that this is a limitation of their study:

First, diagnoses in the NAMCS are based on the independent judgment of the treating physician rather than on an independent objective assessment. For this reason, the data represent patterns in the diagnosis of bipolar disorder rather than patterns in the treated prevalence of the disorder.

In other words, what we have here is a study of doctors’ diagnostic behaviors, not of actual bipolar disorder prevalence rates. This is a component most of the mainstream media is either missing or simply not reporting.

Second, no information is available concerning the dosage of the prescribed psychotropic medications. Third, data from the NAMCS are cross-sectional and therefore do not permit examination of duration and succession of treatment trials. Fourth, sample sizes limit efforts to evaluate the independence of associations between patient demographic and clinical characteristics and provision of psychotropic treatment. Fifth, the NAMCS records visits rather than individual patients, and the number of duplicated data for individual patients is unknown.

Wow, that’s a pretty big red-flag. If you don’t know how much duplicated date you have in your dataset, how can you be certain it’s “good” data to begin with? I guess this is just accepted as a problem with the NAMCS dataset, and researchers go on their merry way analyzing the heck out of it anyways. Seems a bit of a risk though.

The other reason this study appears a little out of whack is because other research shows a far more linear curve for the diagnosis of bipolar disorder in children and teens. For instance, Blader et al. (2007) showed earlier this summer that–

Population-adjusted rates of hospital discharges of children with a primary diagnosis of BD increased linearly over survey years. The rate in 1996 was 1.3 per 10,000 U.S. children and climbed to 7.3 per 10,000 U.S. children in 2004.

A much more modest five and half-fold increase rather than the 40-fold increase the present study found. The results aren’t exactly equivalent, since Blader was looking at inpatients, not outpatients. But you’d expect data that was similar, not wildly out of synch with one another. This type and scope of increase have been held up in other study’s data as well (see, for example, Mandell et al., 2005).

Last reviewed: By John M. Grohol, Psy.D. on 4 Sep 2007 Published on PsychCentral.com. All rights reserved.

About John M. Grohol, Psy.D.

Dr. John Grohol is the founder & CEO of Psych Central. He is an author, researcher and expert in mental health online, and has been writing about online behavior, mental health and psychology issues -- as well as the intersection of technology and human behavior -- since 1992. Dr. Grohol sits on the editorial board of the journal Cyberpsychology, Behavior and Social Networking and is a founding board member and treasurer of the Society for Participatory Medicine.